RESEARCH PROJECT 2 ABSTRACT Project 2 of the ?Maternal and Developmental Risks from Environmental and Social Stressors? (MADRES) Center will examine the effects of multiple pre- and postpartum environmental exposures to air and other chemical pollutants on maternal gestational weight gain and postpartum weight retention. Increasing rates of maternal overweight and obesity before, during and after pregnancy pose serious health concerns for both mothers and children. Beyond diet, physical activity, and genetics, a growing body of evidence implicates the role of environmental exposures in contributing to obesity and related metabolic and cardiovascular diseases. However, there is a lack of research on the etiological role of environmental exposures in maternal gestational weight gain and postpartum weight retention. The burden of exposures to multiple environmental chemicals, many of which are obesogenic, is disproportionately carried by Hispanics in California. These data highlight a striking environmental and health disparity affecting Hispanics that is not well understood. To address these gaps, we propose a novel conceptual model whereby pre-and postpartum environmental exposures, coupled with exposures to social stressors, lead to excessive maternal gestational weight gain and postpartum weight retention through altered psychological and behavioral responses. We will test this model in a longitudinal study of 750 primarily Hispanic, low-income pregnant women who will undergo assessments of environmental exposures (e.g., regional NO2, PM2.5 O3; near-roadway NOx; water contaminants; toxic releases), social stressors (e.g., neighborhood crime, violence, income inequality), psychological (e.g., perceived stress and salivary cortisol) and behavioral (e.g., physical activity and diet) responses, and weight outcomes during pregnancy (1st, 2nd, 3rd trimesters) and postpartum (3, 6, 12 months). In a subset of women (n = 60), we will use innovative personal, real-time data capture strategies (e.g., ecological momentary assessment, personal exposure sampling, location monitoring, accelerometry) to examine day-level effects of exposures on psychological stress and energy-balance behaviors. We hypothesize that (1) greater cumulative pre- and postpartum environmental exposures will be associated with an increased likelihood of excessive gestational weight gain and postpartum weight retention, respectively; (2) exposures occurring during the first trimester of pregnancy will have larger effects on maternal gestational weight gain and postpartum weight retention; (3) effects will be larger in women with greater social stressors, (4) psychological and behavioral responses will mediate these effects; and (5) on any given day, greater personal environmental exposures and social stressors will be associated with greater perceived stress and cortisol, lower physical activity, and unhealthy dietary intake. Results will identify key mechanistic targets for policy, clinical, and programmatic intervention. Given the serious long-term health consequences of excessive gestational weight gain and postpartum weight retention for both mothers and children, this study could have broad-reaching public health impacts.